Dear colleagues

I met the positive sidewall of SU8 when I tried to get the holes array of
SU8 for electroplating. The hole is with diameter of 6 micron and height of
15 micron. What I got is 5.5 micron on the top and 6.2 micron on the bottom.

The processes are as below:

Bake the ITO glass at 120 C for 30 min.
Spincoating 500 rpm for 5 s and 3000 rpm for 40 s.
Rest 10 min.
Softbake: 65 C for 2 min and then 95 for 3 min.
Exp: 224 mJ/cm2(1.5X standard dose according the datasheet)
PEB: 50 ramp up to 65 holding 2 then ramp up to 95 C holding 2 min.
Develop in ultrasonic bath with SU8 developer for 3-4 min then rinse with
fresh developer for 10 s Hard bake: 200 C for 30 min and then cool down to
50 C on hotplate.

The slow ramping up PEB and hard bake were adopted to enhance the adhesion
between SU8 and ITO. I also tried using Cr/Au seed layer on Si wafer but the
adhesion is very poor. SU8 whelm up after plating few min.

Do you think the positive sidewall was caused by hardbake? Any others
comments are appreciated.

Regards
XiaoQiang
Robust1972@gmail.com